The Problem

Most NVMe SSDs have a power saving mode called APST (Autonomous Power State Transition) in which, if sat properly the drive will suspend at some periods of time to save power, while the computer is on, on suspend and hibernate it turns off to save more power, but that’s not the case.

The thing is, that some drives are programmed to ignore this power switching, and with the default kernel parameter of 100,000µs i.e 0.1s, that is the drive’s timeout before going back from power saving mode, in which causes the drive to stay in the power saving mode, and freezes, which is bad, and can occur after a very short time from boot up (if there weren’t much IO operations)

More details in this stack exchange post.

The Solution

Nothing fancy, it’s just a workaround to disable APST, in which the drive stays on as long as the OS says so (i.e. not suspended or hibernated)

All what we have to do is set that parameter to 0, which according to the NVMe driver in the Linux kernel, disables the feature.

In the file /etc/default/grub (you need root privileges to modify it) add the following to he GRUB_CMDLINE_LINUX_DEFAULT variable

GRUB_CMDLINE_LINUX_DEFAULT="nvme_core.default_ps_max_latency_us=0"

If the variable itself have any existing values, just add a space after the last value and add the magical parameter setter, e.g.

GRUB_CMDLINE_LINUX_DEFAULT="snd_hda_intel.dmic_detect=0 nvme_core.default_ps_max_latency_us=0"
# the snd_hda_intel.dmic_detect=0 is an example don't add it unless you know exactly what you're doing

Now save the file, and update GRUB

sudo grub-mkconfig -o /boot/grub/grub.cfg

Some distros name the grub binary as grub2 like Fedora, or openSUSE, in that execute this command instead

sudo grub2-mkconfig -o /boot/grub/grub.cfg

Finally, reboot and your NVMe should be back on track, grinding those 1.5GBps IO speeds.

To double-check (a typo could cause this not to work), check the current value of the latency parameter

cat /sys/module/nvme_core/parameters/default_ps_max_latency_us

If it prints a value other than 0, double check /etc/default/grub, or regenerate the GRUB config again.

NOTE: this was the configuration for GRUB, i.e if you have LILO or Systemd-boot, or any bootloader other than GRUB you might to look up how to add a kernel parameter for that particular bootloader, other than that it’s pretty straight forward.

Quote of the day

“Success lasts until someone screws them, failures are forever”
- Gregory House